Expandable structures of a type similar to that of the present invention are not uncommon. Truss structures of various angular configurations have been deployed and used in a wide variety of construction projects and are particularly adapted to constructing large space structures, such as space stations and space satellites having a requirement for deployable elements. The basic object of such stuctures is to provide a means within the design of the structure to expand from a relatively small package to a relatively large structure. Typically the design includes a core element or cell of arms or links which can be used as the basic modular building block to construct expandable or deployable structures of varying shapes and sizes. The ultimate structure then is designed to be rapidly deployable into a rigid, usable construction structure and is to be equally rapidly retractable into a very small package relative to the structure available when fully deployed. In the past the truss structures that have been conventionally designed have been designed for limited or single purpose uses and have offered therefore little in the way of versatility and adaptiveness to a wider variety of construction or similar structural problems. In addition the conventional design has not always provided for a high compaction ratio above one in the order of 100 to 1 from deployed structure to retracted structure and hence the lower compaction ratio has limited the availability of such deployable structures to large structural uses. One typical expandable and retractable structure is described in U.S. Pat. No. 3,771,274 issued to Desmond H. Vaughan. The Vaughan patent describes a structure which comprises a first set of three rigid links connected by a first primary pivot point and a connected set of three rigid links connected at a second pivot point. The second set of links is joined to the first set of links by three secondary pivot points. To create or deploy the structure a set of three bracing cables is employed to connect between and to the three secondary pivots and thereby complete a double tetragonal structure. An actuator system is provided in the form of an extension cable 51 inside arm 52 which is designed to draw together the two primary pivot points, thereby rigidizing and stabilizing the basic cell and the deployed structured formed from a plurality of these basic cell forms. To collapse the structure the three bracing cables 10, 11, and 12 are drawn inwardly and the three pivot points are drawn together to collapse the structure into a very simple shape.
A similar structure is shown in the patent issued to Paul Slysh in U.S. Pat. No. 4,337,560 which describes a method for assembling large space structures. The space structure shown therein, comprises a plurality of trusses and truss junctions which in turn are made up of a plurality of individual struts and nodes. The basic cell structure formed by the assembly of struts and nodes is a three-dimensional element in which each end face is triangular and each of the three side faces is rectangular. The triangular structure employs arms 12 connected between two sets of three pivot points at each end face and each side is formed by additional arms 12 connected between each of the corresponding pivot points of the two sets. In addition, each of the side faces has an additional leg 12 diagonally disposed and connected between one pivot of each of the two sets of cells to act in bracing the structure. The Slysh patent however, is directed primarily to the method for assembling these structures using these types of cells and is not concerned generally with the particulars of a design for rapidly deploying or collapsing the resulting structure to a compact package, but rather has directed its inventive skill to the individual arms 12 and the adaptability of these arms to a variety of such structures built upon this particular triangular shaped cell.
One example of a design for only a single use in this art is that shown in U.S. Pat. No. 4,017,932 issued to S. Lotto, et al. The Lotto patent describes a temporary, modular, self erecting bridge which can be transported from place to place upon collapsing the side, top and bottom elements above respective pivot points. The expansion and contraction of these elements is effected by hydraulic jacks that are strategically positioned to draw in the several elements and cause the pivoting. The cell structure, however, is generally a simple triangular element with no bracing beyond that provided by the hydraulic jacks, and hence the design of any structure formed from this triangular shape relies on the placement of these hydraulic jacks.
Additionally, U.S. Pat. No. 4,276,726 issued to D. L. Derus, describes a collapsible, articulated wall structure which is formed from pivotally interconnected links. The basic structure is that of a three-dimensional rectangular or square cube formed from six pairs of crossed links that form each face of the cube and in which the individual links are connected from corner to corner and from pivot point to pivot point. The collapsible nature of the structure is effected by means of a single, fixed x-shaped element 70 which is designed to pivot inwardly after it is unlocked to allow the crossed links formed by link 70 to collapse downwardly as the respective pivot points to which they are attached are drawn in. The remaining sections draw into a fairly compact unit as shown in FIG. 4 of Derus.
The present invention comprises, as do most of the prior art devices, a plurality of legs or links interconnected between a plurality of pivot points. The present invention is unique however in that it uses a pyramidal shape pair of cells as the basic modular core for building upon, and in that it employs a diagonally-acting member to effect the tensioned or erected state and can be collapsed by the pivot arms of several of the links pulling in upon each other. In addition, the peculiar arrangement of the design enables it to achieve a normal contraction ratio in the order of 280 to 1, far greater than that achieved by designs shown and described in the prior art.
Accordingly, it is an object of the invention to provide a very high contraction-ratio structure that is employable in a variety of rapidly deployed and rapidly collapsed structures particularly for use in construction of structures, that serve a variety of purposes.
It is also an object of the present invention to provide for a structure that employs a pyramidal shaped cell as the basic modular core upon which the entire structure can be built.
It is another object of the present invention to provide for three varying types of legs or structure elements, one type being designed to carry the main structural load as required for the particular end use, another being employed to allow for an extremely high contraction ratio by having a pivot point along its length, and a third type employed to tension or contract the pyramidal shaped cell. In the deployed state, the diagonal actuation member, the third type employed therein, acts to strain the structural members, the joist type, in such a way that no compression load is sustained by the members having the articulated pivot joints, the second type.
It is a further object of the present invention to provide a structural deployment means which provides for the simultaneous activation and retraction of a plurality of diagonal actuation members for a plurality of modular, pyramidal shaped cells to form a rigid reinforced structure varying in size and complexity.
Equally, it is an object of the invention to provide a means for storage which only requires the simultaneous extension of the same diagonal actuation members to effectively retract the structure into an extremely compact state.
It is a further object of the present invention to facilitate both the deployment and retraction of the modular, pyramidal-shaped cells used in a structure through the use of a motorized cable reel assembly which is designed to manipulate the diagonal actuating members through a centralized point.